I'll back you up one step, and that's with your waterproofing. Hydroban is indeed a water barrier, but not a vapor barrier.

With the vapor drive in a steam shower, you'll want to use something else. I usually recommend Kerdi, as that's my membrane of choice in a steam shower. But there are others as well. If you want a roll-on like Hydroban, then look at RedGard.

When you do your water/vapor proofing, your walls will probably be cement board over studs. The cement board will usually stop just above the flange of the pan. You carry your membrane from the cement board and on to the flange of the pan. That creates a complete barrier.

Take a look at this thread and scroll down about 2/3rds of the way through it until you see a couple of hand drawn depictions. Though the drawings were for a tub, the idea is the same.

As a reminder, you'll want the Kerdi or RedGard or whatever vaporproof membrane you use to be on all walls and the ceiling.

Before we move on to the plumbing, does that make sense?

Hi Mongoct. We are just building a normal shower, not a steam shower - so I was thinking that Hydroban would be simpler than Kerdi (and perhaps less expensive), especially since we plan to build a niche (all the pieces required to Kerdi a niche scare me off). I realize that with a membrane like Kerdi it could go on to the flange of the pan (but then if you silicone the bottom of the tile won't it prevent the water escaping?), but how do you extend the waterproofing on to the pan, if you are painting on Hydroban? I have searched and searched, and nothing seems clear.

Should I/can I add a small strip of Kerdi to the bottom of the cement board to continue the waterproofing to the flange? If I did so, would I apply it on top of the HB, or not apply HB to that small bottom part of the cement board?

Thanks for your help!

P.S. I had bookmarked your original Kerdi how-to when you first wrote it....(sadly that tells you how long we've been planning this bathroom reno...)

Oh wow. You may be suffering from reno weariness, I think I'm just getting plain old delusional.

When I first read your thread title I somehow read "steam shower". No kidding. It...was...there...lol

I just finished one so maybe my mind is on that topic.

So...ignore everything I wrote! lol

Hydroban will be perfect for your shower. Stick with it. No need for Kerdi.

I'll pull one of the drawings over here just for visualization. You can do it the same as in this drawing, except:

1) The Kerdi will be Hydroban
2) You don't need the Kerdi-Fix

The time to be concerned about drainage behind the tile is when using a poly barrier behind cement board. With a topical membrane like HB, there will be no deep wetting of the substrate.

Any moisture that was able to wick through the grout and get into the thinset will simply evaporate out through the same path during the shower's drying cycle.

So it's not a problem at all to caulk the gap between the bottom course of tile and the pan.

If you were to use the method in the other drawing (no furring strips), then after the cement board is installed, fill whatever small or uneven gap there is between the pan's flange and the cement board with stiff thinset. After it cures, hydroban from the cement board, over the fill, and onto the flange. That will give you a continuous barrier.

Again, sorry for the steam shower mis-read.

Oh, thank you so much! I know Google can be your friend, but really, have not been able to find ANYTHING to answer my concerns as well as you just have! I think we will do the non-furring strip method and thin-set the bottom and then HB.

Now, my next concern, I am thinking of putting up 12 X 24 porcelain tiles (limestone lookalikes). We have only ever tiled backsplashes, and the largest tile we've used was 4 X 12. DH is an engineer and we will gut the existing walls and install the cement board ourselves. I know it is imperative to get them as flat and level as possible, any tips? I guess I will also have to remove the existing tar-paper backed fibreglass, Any suggestions as to what to replace it with? (I know I don't want a vapour barrier behind the cement board).

Now, when we install the tile, how do we know how close we can place the individual tiles together? I've heard the term rectified, but it doesn't say that on my sample board...though the tile is very straight and not slanted on the edge like another porcelain sample I have. The store told us to do the 33 1/3% stagger to minimize lippage/warpage problems that these larger tiles have?

Here is a link that might be useful: limestone looking porcelain tile

If this is an exterior wall and you are in a heating climate, then you'll still want a vapor barrier on the living space side of that wall. The key is to not have two vapor barriers on the same wall. But remember, HB is not a vapor barrier.

So when you gut it to the studs, you can reinsulate with unfaced FG batts if FG is your insulation of choice. Whenever using FG, I'll use unfaced batts. I then cover that with 6-mil polyethylene, stapled to the studs. The poly gives a continuous barrier, a much more effective barrier than faced insulation.

You are correct...with the large tiles, you'll want your walls flat, plumb, and your corners square. "Flat" and "plumb" will give you nice corners.

After you gut to the studs, you can simply use a level to make sure that the corner studs are plumb. The you can run a level, a straight edge, or use a string, to make sure that the wall itself it flat and all studs are in plane.

If you have small discrepancies, the offensive studs can be shimmed or planed. If the wall is really wacky, then sometimes it's best to restud the wall by sistering new studs to the old.

With the studs on plane, you then do your plumbing and electrical as needed and then hang your cement board.

Where people go wrong is when they tape and thinset the seams of the cement board they leave too much thinset on the joint and create a hump. All you want to do is fill any gaps with thinset so the HB can bridge from one piece of cement board to the next. That's it.

Rectified tile is tile that is fired in very large sheets and then cut to size. So the tiles are usually quite flat, have sharp sawn edges (like a marble tile would have), and they are pretty much exactly the same size.

Non-rectified tiles are cut to size then fired. So the clay can shrink a little here or warp a little there during the firing process.

Take a stack of several tiles and set them on edge, like a deck of cards. Square up two edges. The other two edges will show any discrepancy in tile sizing.

In general, a rule-of-thumb of sorts is that you want your grout lines to be 3 times the size differential. If your tiles were off by 1/16" in size, then you'd shoot for a 3/16" grout lines.

The old guideline used to be 1/16" minimum grout width. That's been changed to 1/8".

Can you go smaller? Sure, but it could slow down the installation. It really is dependent on the tile. Flat. Warped. Square. Pillowed. Bowed? The wackier the tile, the more difficult it is to get a good installation with small gout lines.

Rectified tiles, being uniform in size, can usually be set closer together than nonrectified. Another thing is tile size, specifically the size you are using. With the proliferation of long rectangular tiles like your 12" by 24" tiles, lippage from bowed tiles can be a concern.

Example, stack two of your 12 by 24s and then flip them up on edge. Do they nestle nicely against one another? Now flip one tile over so they are glaze-to-glaze. Do they still nestle tightly together or do they rock against each other?

Longer tiles like that can have a bow or an arch in them. That's why your tile shop gave you guidance regarding the 33% offset. If you did a straight 50% offset staggered brick pattern, the high point of each tile's arch would be next to the ends of the neighboring tiles. Any bow in the tile would show as lippage between adjacent tiles. Reducing the offset to 33% or 25% reduces lippage.

All that being said, lippage is always a concern. But it's more a concern on floors than walls. I had a job years ago where the homeowner wanted flaws in the wall tile. They wanted it to look imperfect, a little rustic, they wanted lippage. On a floor I'd never do that.

And...one other comment.

In your proposed list it looks like you have a fixed shower head, a handheld, and four body sprays.

Now I'll be a stickler here and give you a literal interpretation of the building code. Your inspector may or may not. But code cares about one thing; how many outlets are in the shower. With that list, you have six. Code does not care how many can flow at once. Code does no care about diverter valves. Code only cares how many outlets there are.

You can have up to three outlets with a single 2" drain in the shower. For your six outlets, you'd need a single 3" drain or two 2" drains. Your drain line under the floor would have to be increased from 2" to 3" as well.

Again, will your inspector call you out on that? I have no clue. Some are sticklers for code, some don't even know the code. But I thought I'd point that out to you just in case.

Wow, thanks so much Mongoct! You explain things so well, and so clearly, that I can feel the tension releasing from my shoulders as I type. So, if we waterproof with Hydroban, we will still need a vapour barrier between the FG and the cement board? So, could we reuse the tar-paper backed FG that is there now, and add a plastic vapour barrier? Not sure what DH is planning, I am guessing he would want to put in new FG, whereas I like to reuse where possible. Is there any benefit to throwing out the old FG and replacing it? The stuff that I can see (have only gutted half) looks fine, not even dirty like FG was on other walls of house.

I talked to DH about drain. He is planning on using 2 1/2". I am not firmly committed to body sprays yet (have no experience with them), but am imagining they might be nice. We will look into code here, may be different? What do people do with the shower panels I see? I am assuming they are often used for retrofit, so am guessing no change in drain size?

You're welcome!

Insulation: If your existing FG is in fine shape, then sure, leave it as is. If the paper facing on it gets dinged up during the demo to where there are holes and tears in it, then just slash the remainder of the paper facing here and there with a utility knife, THEN cover the entire wall with the 6-mil poly.

Aside: Dirty FG is usually due to air infiltration, when air moves through the FG the FG essentially acts like an air filter, filtering out airborne particles. If you find dirty FG look for holes or gaps nearby, and fill them with canned foam.

Body Sprays: I'll tell you that I'm not a big fan of body sprays, I just find them impractical. I've stayed in resorts and hotels that had them, my wife even thought them superfluous. She could have had anything she wanted in the shower in our master bath, she nixed body sprays right off the bat. Don't let that scare you away from them if it's something you want. That is simply our opinion.

The Drain: The six heads versus the 2" drain? No longer an issue for you if your husband is using a 2-1/2" drain and branch line. Six outlets is fine for a 2-1/2" system.

The Conclusion: You two are way ahead of me!